Molecular epidemiology of Neisseria gonorrhoeae in Amsterdam, The Netherlands, shows distinct heterosexual and homosexual networks

Abstract

Molecular typing, added to epidemiological data, can better identify transmission patterns of gonorrhea in Western countries, where the incidence has recently been rising. From September 2002 to September 2003, patients with a laboratory-confirmed diagnosis of gonorrhea at the Clinic for Sexually Transmitted Infections in Amsterdam, The Netherlands, were subjected to a questionnaire pertaining to sexual risk behavior and sexual partners in the 6 months prior to the diagnosis. The Neisseria gonorrhoeae isolates were all genotyped using PCR-restriction fragment length polymorphism of the porin and opacity genes. All patients with a completed questionnaire and genotyped isolates were included in the study. We obtained 885 N. gonorrhoeae isolates from 696 patients that revealed 88 clusters and 46 unique genotypes. Patients infected at multiple anatomical sites with one or more strains and patients infected several times during the study period were shown to pursue high-risk sexual behavior and were considered core groups. There were 11 clusters of > or =20 patients; in seven clusters, 81% to 100% of patients were men who have sex with men (MSM), three clusters contained 87 to 100% heterosexual men and women, and one cluster was formed by equal proportions of MSM and heterosexual male and female patients. However, the various clusters differed in characteristics such as types of coinfections, numbers of sexual partners, Internet use to seek sexual partners, and locations of sexual encounters. Molecular epidemiology of gonococcal isolates in Amsterdam revealed core groups and clusters of MSM and heterosexual patients that probably indicate distinct transmission networks.

FIG. 1.

Genetic diversity among all large por-opa clusters (≥20 gonorrhea patients) as shown in a phylogenetic tree constructed for two N. gonorrhoeae isolates from each large cluster of gonorrhea patients at the STI Clinic in Amsterdam, The Netherlands. POR MspA1 I, RFLP patterns of por with restriction enzyme MspAlI; OPA Taq1, RFLP patterns of opa with restriction enzyme TaqI; Isolate nr., isolate number; Location, anatomical site of culture; C, cervix; R, rectum; T, tonsil; U, urethra; Date, date of visit to STI clinic (year-month-day); poC, por-opa cluster number. Numbers indicate the sizes of the clusters in the phylogenetic tree. The scale in the upper left-hand corner shows the percentage of similarity between the RFLP patterns of por and opa genes.

FIG. 2.

Cluster F6 of gonorrhea patients at the STI Clinic in Amsterdam, The Netherlands. The symbols following the cluster numbers (> and !) represent two isolates of multiple anatomical sites (tonsil and urethra) obtained from one individual at one visit. @ indicates two isolates from a recidivist with two isolates in the same cluster obtained at two different visits. For abbreviations, see the legend of Fig. 1.

FIG. 3.

Example of one gonorrhea patient (§) found to be infected with three N. gonorrhoeae strains (tonsil, rectum, and urethra) at one visit to the STI Clinic in Amsterdam, The Netherlands. The three isolates belong to clusters A7, G3, and U2; all isolates of these clusters are shown in one phylogenetic tree. See the legend of Fig. 1 for abbreviations.